We are continuing to study the interaction of gonadal hormones and behavior in a social context and evaluating the specific interaction of prior social experience and social context upon the influence of altered status of hormones upon behavior and the influence of behavioral manipulations upon hormones. In the next year we will examine the effect of "group formation" phenomena upon male and female gonadal hormones and their sexual behavior as it interacts with seasonal factors. Three heterosexual groups of rhesus monkeys will be reorganized during the hormonally transitional season for rhesus males. Dominance rank changes, hormonal responses to such social dynamics and sexual and agonistic behavior will be monitored and correlated with seasonal changes. In addition, selected males in two rhesus groups will be castrated at the close of the breeding season to initiate a long term study of the effects of altered hormonal levels upon behavior and the interaction with seasonal factors in stable normal heterosexual groups. Rank changes, alterations in patterns of sexual, agonistic and play behavior will be studied along with the effect of seasonal factors on the group and the castrated males.